White matter integrity correlates of implicit sequence learning in healthy aging.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Aging Research

Background:

• Implicit sequence learning involves subcortical and cortical brain regions.
• Previous studies show mixed results on age-related differences in these neural substrates.
• White matter connections supporting these regions are not well understood in aging.

Purpose of the Study:

• To investigate white matter tract integrity in implicit sequence learning using diffusion tensor imaging (DTI).
• To examine age-related differences in brain-behavior relationships for sequence learning.
• To determine if white matter integrity mediates age-related learning differences.

Main Methods:

• Diffusion tensor imaging (DTI) tractography was used to reconstruct white matter pathways.
• Tract integrity was correlated with performance on the alternating serial reaction time task (ASRT).
• Participants included younger and healthy older adults.

Main Results:

• Both age groups demonstrated significant sequence learning on the ASRT.
• Sequence learning showed an age-related difference in the late learning stage.
• Caudate-DLPFC and hippocampus-DLPFC tract integrity correlated with ASRT learning, irrespective of age.
• Reduced caudate-DLPFC tract integrity mediated age-related differences in late-stage learning.

Conclusions:

• White matter tract integrity plays a key role in implicit sequence learning.
• Brain-behavior relationships for sequence learning are similar in younger and older adults.
• Age-related decline in caudate-DLPFC white matter integrity contributes to learning differences in aging.